<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  .app {


    display: flex;
    background-color: pink;
  }
  .box1 {
    width: 300px;
    height: 300px;
    background-color: yellow;
    /* 元素本身没有移动，而是右侧的外边距margin 缩小了100px, 会导致右侧的元素想左移动100px */
    margin-right: -100px;
    /* 元素本身没有移动，而是下方的外边距margin 缩小了100px, 会导致下方的元素向上移动100px */
    margin-bottom: -100px;
  }
  .box2 {
    width: 300px;
    height: 300px;
    background-color: rgb(47, 83, 215);
    /* 向上移动100px */
    margin-top: -100px;
    /* 向左移动100px */
    margin-left: -100px;
  }
  .box3 {
    width: 300px;
    height: 300px;
    background-color: red;
  }
</style>
<body>
  <div class="app">
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
  </div>
</body>
</html>